This invention relates to an air bag apparatus to be mounted on a vehicle such as an automobile for the protection of a passenger thereof.
The air bag apparatus comprises an air bag, an inflating means and an acceleration sensor for controlling the inflating means. At the time of crushing of the vehicle, the inflating means is applied with electric current by the acceleration sensor to generate a gas, thereby inflating the air bag. As the air bag apparatus for the driver's seat, there is conventionally known one in which the air bag and the inflating means are disposed on a steering wheel. In such an arrangement, it is normal practice to dispose the acceleration sensor in a front portion of the vehicle and to electrically connect it to the inflating means by means of a harness.
There is also known one in which the inflating means is mechanically ignited through the acceleration sensor (see Japanese Published unexamined patent application No. 248454/1985). In this case, the air bag, the inflating means and the acceleration sensor are naturally disposed closely to each other in one place.
In case of the one in which the inflating means is electrically ignited, it is preferable to construct the air bag unit by closely disposing the air bag, the inflating means and the acceleration sensor in one place when the simplicity of the electric wiring and the ease of mounting on the vehicle body are considered. In either type of electrical and mechanical ignition of the inflating means, it is preferable to provide a plurality of acceleration sensors in order to increase the reliability. However, if the plurality of acceleration sensors are closely disposed in a single place, they are placed in one and the same environmental conditions, thereby giving rise to a possibility of their going out of order all at the same time.